# How can I convert a SymPy expression to NumPy?

How can I convert a sympy expression to numpy code? For example, say I this was the code for the expression:

``````expression = 2 * x/y + 10 * sympy.exp(x) # Assuming that x and y are predefined from sympy.symbols
``````

I would want to go from `expression` to this:

``````np_expression = "np.dot(2, np.dot(x, np.linalg.pinv(y))) + np.dot(10, np.exp(x))"
``````

Note that `x` and `y` are matrices, but we can assume the shapes will match

An example with real numbers would go like this:

``````a = np.array([1,2],[3,4])
b = np.array([5,6],[7,8])

expression = 2 * a/b + 10 # These would be sympy symbols rather than numbers
``````

and the result would be this:

``````np_expression = "np.dot(2, np.dot(5, np.linalg.pinv(9))) + 10"
``````

### >Solution :

``````In [1]: expr = 2 *x/y + 10 * exp(x)
In [3]: f = lambdify((x,y), expr)
In [4]: help(f)
_lambdifygenerated(x, y)
Created with lambdify. Signature:

func(x, y)

Expression:

2*x/y + 10*exp(x)

Source code:

def _lambdifygenerated(x, y):
return 2*x/y + 10*exp(x)
``````

Which for specific inputs, array or otherwise:

``````In [5]: f(np.arange(1,5)[:,None], np.arange(1,4))
Out[5]:
array([[ 29.18281828,  28.18281828,  27.84948495],
[ 77.89056099,  75.89056099,  75.22389432],
[206.85536923, 203.85536923, 202.85536923],
[553.98150033, 549.98150033, 548.648167  ]])
In [6]: f(1,1)
Out[6]: 29.18281828459045
In [7]: f(2,3)
Out[7]: 75.22389432263984
In [8]: f(np.arange(1,4),np.arange(1,4))
Out[8]: array([ 29.18281828,  75.89056099, 202.85536923])
``````

Normal array broadcasting rules apply. Note that `x/y` is element-wise. I’m not sure what `lambdify` will translate into `dot` and `inv` code.

trying your `numpy` code:

``````In [9]: np.dot(2, np.dot(2,np.linalg.pinv(3)))+10*np.exp(2)
---------------------------------------------------------------------------
LinAlgError                               Traceback (most recent call last)
<ipython-input-9-6cae91f0e0f8> in <module>
----> 1 np.dot(2, np.dot(2,np.linalg.pinv(3)))+10*np.exp(2)
....

LinAlgError: 0-dimensional array given. Array must be at least two-dimensional
``````

We have to change the `y` into a 2d array, e.g. `[[3]]`:

``````In [10]: np.dot(2, np.dot(2,np.linalg.pinv([[3]])))+10*np.exp(2)
Out[10]: array([[75.22389432]])
``````